A photographic technique wherein a photographically useful photographic reagent is previously incorporated in a silver halide photographic material and the effect of the photographic reagent is utilized during processing has different features than a technique using such a photographic reagent by incorporating it in a processing solution. These features are that: (1) a photographic reagent which is easily decomposed by the action of an acid or an alkali or under an oxidizing or reducing condition, and thus cannot be stored in a processing bath for a long period of time, can be effectively utilized; (2) the composition for the processing solution can be simplified and can be easily prepared due to the absence of the photographic reagent in the processing solution; (3) a photographic reagent necessary for a specific photographic layer and/or an adjacent layer to the layer only of a multiplayer photographic material can function for the layer(s) only, and (4) the existing amount of a photographic reagent can be changed as a function of the development of silver halide in a silver halide photographic material.
In this case, however, if a photographic reagent is incorporated in a silver halide photographic material in an active form, the reagent sometimes reacts with other components in the photographic materials or is decomposed by the action of heat, oxygen, etc., during the storage of the photographic material before processing, whereby the expected effect of the photographic reagent cannot be obtained during processing.
As a method of overcoming such a problem, there is a method of blocking the active group of a photographic reagent and incorporating the reagent in a photographic material in a substantially inactive form, that is, incorporating the photographic reagent in a photographic material as a precursor of the reagent. When the photographic reagent is a dye, there is an advantage that by blocking a functional group of a dye having a large influence on the spectral absorption of the dye to shift the spectral absorption thereof to a shorter wavelength side or a longer wavelength side, the reduction in sensitivity by a so-called filter effect does not occur even when the dye exists in a silver halide emulsion layer having the light-sensitive spectral region corresponding to the spectral absorption of the dye.
When the photographically useful photographic reagent is an antifoggant or a development restrainer, the adhesion thereof to light-sensitive silver halides and the desensitizing action thereof by the formation of silver salt during the storage of the photographic material containing the reagent can be restrained by blocking the active group of the photographic reagent, and, at the same time, the incorporation of the photographic reagent in a photographic material has advantages such as that by releasing the photographic reagent from the photographic material with appropriate timing, the formation of fog can be reduced without reducing the sensitivity of the photographic material, the occurrence of overdevelopment fog can be restrained, and/or the development can be stopped at the appropriate time.
When the photographically useful photographic reagent is a developing agent, an auxiliary developing agent, or a fogging agent, there are advantages such as that by blocking the active group or adsorption group of the photographic reagent, the occurrence of various photographically undesirable events, such as the formation of semiquinones or oxidized materials by air oxidation during the storage of the photographic material can be prevented, or the formation of fogged nuclei during storage of the photographic material can be prevented by preventing electron injection into silver halide, which results in stable processing.
When the photographic reagent is a bleach accelerator or a blix accelerator, there are advantages such as that by blocking the active group of the photographic reagent, the occurrence of reactions thereof with other components contained in the photographic material at storage thereof can be restrained, and by releasing the blocking group during processing of the photographic material, the desired effect of the photographic reagent can be utilized at the appropriate time. Groups known in the art by the various terms such as active group, functional group, and adsorption group are commonly referred to herein as "active group".
As described above, the utilization of a precursor for a photographic reagent can be a very effective means for sufficiently exhibiting the performance of the photographic reagent, but, on the other hand, the precursor must meet very severe conditions. That is, the precursor must satisfy the factors, which are somewhat inconsistent with each other, that the precursor stably exists in the photographic material under storage conditions, but that during processing, the blocked group of the photographic reagent is released at the appropriate time to quickly and effectively release the photographic reagent.
Various blocking techniques for photographic reagents are known. For example, there is a method of utilizing a blocking group such as an acyl group, a sulfonyl group, etc., as described in U.S. Pat. No. 3,615,617 (Japanese Patent Publication No. 44,805/72); a method of utilizing a blocking group releasing a photographic reagent by a so-called reverse Michael reaction as described in U.S. Pat. Nos. 3,674,478, 3,791,830, and 4,009,029 (Japanese Patent Publications Nos. 39,727/79, 9696/80 and 34927/80); a method of utilizing a blocking group releasing a photographic reagent with the formation of quinonemethide or a quinonemethide-like compound by the electron transfer in the molecule as described in Japanese Patent Publication No. 39,727/79, Japanese Patent Application (OPI) Nos. 135,944/82, 135,945/82, and 136,640/82 (the term "OPI" indicates an unexamined published patent application open to public inspection); a method of utilizing the intramolecular ring closing reaction as described in Japanese Patent Application (OPI) No. 53330/80; and a method of utilizing the cleavage of a 5-membered or 6-membered ring as described in U.S. Pat. No. 4,335,200 (Japanese Patent Application (OPI) No. 76,541/72) and Japanese Patent Application (OPI) Nos. 135,949/82 and 179,842/82.
However, these known photographic reagents blocked by a blocking group have a problem in that the releasing speed of the photographic reagents cannot be widely controlled, and hence the usable pH range is limited. That is, in the photographic reagent which is stable under storage conditions for the photographic material containing the agent, the releasing speed of the photographic reagent is too low, and processing by a high alkaline processing solution having a pH higher than 12 is required for releasing the reagent; on the other hand, photographic reagents showing a sufficient releasing speed during processing by a processing solution having a pH of 9 to 11 tend to gradually decompose under storage conditions, to reduce the function thereof as the precursor.